This invention relates generally to apparatus and methods of repairing a stator bar of a generator, and particularly to apparatus and methods for repairing the stator bar clips.
Water-cooled stator bars for electrical generators include a plurality of small rectangular solid and hollow copper strands which are brazed to one another within the stator bar and brazed to the interior walls of an end fitting. The brazing material typically used is a copper phosphorous alloy. The end fitting serves as both an electrical and a hydraulic connection for the stator bar. The end fitting typically includes an enclosed chamber for ingress or egress of stator bar cooling liquid, typically deionized water. Thus, the end fitting provides a hollow chamber which serves to manifold the water passages of the strands. An opening of the end fitting receives the ends of the strands of the stator bar, the fitting and peripherally outermost copper strands of the stator bar being brazed to one another. A second opening includes a clip for connecting the bar to series loops/phase connections and a cooling water supply. This clip is often referred to as the stator bar bottle clip. Over time, leaks have variously developed about the connection between the stator bar ends and the stator bar end fitting as well as between adjacent strands. The end fitting-to-strand and strand-to-strand joints have the highest potential for causing damage should a leak occur because a leak at this location will flow directly into the ground wall insulation of the winding. The result is the degradation of the dielectric strength of the insulation which will eventually lead to failure. Also, the braised connections between the bar bottle clip to series loops/phase connections and cooling water supply piping can be weakened by excessive tolerances between the fixtures which requires the use of excessive braise alloy thereby causing a weak joint. Further, oversized and elliptical shaped bar clips can cause fitup problems and weak braised joints.